PROJECT SUMMARY/ABSTRACT The purpose of this five year K01 application is to prepare Dr. Sara M. St. George for an independent research career devoted to developing, evaluating, and disseminating innovative, evidence-based obesity prevention interventions for Hispanic adolescents. This project contains three training goals: 1) To advance Dr. St. George's understanding of cultural factors that contribute to obesity and related health behaviors in Hispanic adolescents; 2) To develop her expertise in the design of behavioral intervention technologies (i.e., those that use technologies such as mobile phones to promote behavior change), including the use of human factors/user-centered design approaches to incorporate user perspectives into intervention development; and 3) To enhance Dr. St. George's ability to apply advanced quantitative methods for evaluating randomized controlled trials. To achieve these goals, Dr. St. George has assembled an interdisciplinary mentoring team with expertise in public health, psychology, human factors engineering, behavioral intervention technology, and quantitative methods. Given the paucity of research on family-based obesity prevention interventions in Hispanic adolescents as well as data indicating Hispanics are most likely to access the internet from smartphones, Dr. St. George's research will focus on developing and pilot testing a family-based intervention that uses the web and mobile phones (eHealth) to improve the physical activity, sedentary behavior, and diet of Hispanic adolescents. Two research aims are proposed: 1) To conduct formative research which will inform the development of a family-based eHealth obesity prevention intervention for improving moderate-to-vigorous physical activity, sedentary behavior, and dietary intake in Hispanic adolescents; and 2) To conduct a pilot randomized trial to determine the feasibility, acceptability, and preliminary effects of the intervention. To accomplish Aim 1, Dr. St. George will involve Hispanic parents and adolescents in all stages of the design process by: 1a) conducting four focus groups with 20 Hispanic parents and adolescents; 1b) developing and iteratively testing visual mockups (?paper prototypes?) of the intervention with three groups of 5 Hispanic parent-adolescent dyads; 1c) developing a fully functional intervention prototype; and 1d) conducting a field trial with 10 Hispanic parent-adolescent dyads using the fully functional prototype. To accomplish Aim 2, Dr. St. George will recruit and randomize 50 parent-adolescent dyads from pediatric primary care clinics to a family- based eHealth obesity prevention intervention or a primary care as usual comparison condition. It is hypothesized that the intervention will be feasible, acceptable, and show promising effects compared to primary care as usual in increasing moderate-to-vigorous physical activity, reducing sedentary behavior, and improving quality dietary intake in adolescents at post intervention and a 6 month follow-up. Changes in parent healthy lifestyle behaviors and family functioning will be assessed as secondary outcomes. Data will be used to pursue R01 funding to conduct a large-scale randomized controlled trial.